As is known, these tests can be carried out according to a number of methods which include the use of specific reagents that once in contact with a biological liquid indicate the presence of sought element or elements in it.
Depending upon the type of research and reagent used, the operator will follow methods which differ in length, handling, quantity of reagent to be used and biological liquid to be put in reaction.
For instance, one of the methods most commonly used to determine the blood group of a person includes causing a reaction between blood of that person and an inert substance comprising microgranules of a synthetic material having various diameters hereinafter called "gel" for convenience, and a specific antiserum for the sought antigen.
More particularly, the method used in this case is the following:
a known quantity of gel, to which a specific antiserum for the test to be carried out has been homogeneously added in advance, is placed inside a glass or plastic test tube, PA1 a determined quantity of suitably diluted red globules to be tested is added in the same test tube, PA1 the test tube is located in a centrifuge to allow the red blood globules to mix with the solution previously placed in the test tube, and PA1 should the red globules react with the antiserum in the tube while being centrifugated, they form agglutinates, whereas the gel prevents them from sedimenting at the bottom of the test tube, PA1 should the reaction be optically positive, i.e. should the red blood globules react with the antiserum, no formation of a well defined "button" will occur at the bottom of the test tube, and dispersion of the agglutinates in the solution of the gel located on top will take place. PA1 a known quantity of gel is placed inside a glass or plastic test-tube in which Coombs serum was homogeneously added in advance, PA1 a determined quantity of "haemacies", i.e. panantigenic red globules including all the known antigens in their structure, is added to the same test-tube, PA1 a specific quantity of serum to be tested is added to the same test tube, PA1 the contents in test tube are then left to incubate for a time interval ranging from 10 to 15 minutes, PA1 after incubation the test tube is placed in a centrifuge to be centrifugated at a predetermined speed.
Another method used is that concerning the "Coombs test" and crossed tests.
In that case, the followed method comprises the following steps:
If during incubation and centrifugation steps a reaction has taken place, the result will be agglutination between "haemacies", serum to be tested and Coombs serum.
Also in this case, the gel prevents the agglutinates from forming a well defined "button" in the test tube.
Devices ready for use are available on the market which comprises a series of test tubes (usually six or eight in number that are placed one next to the other and connected to each other by a single plastic support), in which gel (i.e. a support substance for the reaction) suitably mixed with the reagent (such as antiserum, Coombs serum, or another serum) was previously added.
These devices have the definite advantage of offering the operator a device ready for use for carrying out tests, i.e. the test tube does not require to be filled with gel and reagent by the operator, since it is already loaded with such components.
There are, however, numerous disadvantages among which the pre-configuration of the tests. As a matter of fact, the manufacturers of these devices ready for use must necessarily foresee two things: a mininum number of already loaded test tubes to be included in the same device or system--hereinafter called "index card" for convenience--and a given configuration of tests to be carried out on the index card.
A frequent inconvenience of this state of affairs is to be faced when the operator has to carry out only three blood tests, but is going to use an index card which has six or eight test tubes ready for use, and thus he is not going to use more than half of the test tubes available, while the rest are to be disposed unused.
If one takes into account the great number of blood tests (anti-A, anti-B, anti-E, etc.) which are carried out, one will realize that substantial waste occurs, this being especially true in those centers where only relatively few blood tests are carried out.
An alternative solution would be that the operator should wait to carry out blood tests until he has gathered a number of tests at least approximately equal to that or a multiple of the available test tubes in an index card.
Another disadvantage of the "index card" lies in the difficulty in automating the testing procedure described above.
Bearing in mind that several working steps are involved, i. e. introduction of various liquids into the test tubes of an index card, incubation, centrifugation and surveying and reading the test results, a complex and expensive equipment is required.
Document EP-A-0295069 discloses a diagnostic test device for detecting the presence of a component in a liquid sample, comprising a liquid impervious receptacle vented by a liquofobic element. The receptacle houses an absorbent which contacts and draws liquid through a microporous reaction medium, gas being displaced from the absorbent during the liquid absorption.
Document EP-A-0141009 discloses a rotor unit of a centrifugal analyser. The rotor unit is divided into several different elements, each of these elements containing felt members and a pre-packaged reagent which, during the rotation of the rotor unit, is mixed up with the testing sample into a measuring room. The optical absorption measurement is carried out by means of a polychromatic photometer.
Document U.S. Pat. No. 4,226,531 discloses a disposable multi-cuvette rotor for use in an analytical photometer which comprises two injection molded parts from a transparent material of suitable chemical and absorption characteristics. Each of the cuvettes is divided into adjoining sample and reagent/measuring chambers by a wedge-shaped element.